Trimer catalyst system for aliphatic and aromatic isocyanates

ABSTRACT

This invention relates to a novel trimerization catalyst system, and to a process for trimerizing organic polyisocyanates in the presence of thermally active catalyst systems. These catalyst systems comprise (A) compounds selected from the group consisting of (i) lithium salts of aliphatic or aromatic carboxylic acids, (ii) lithium salts of hydroxyl group containing compounds wherein the hydroxyl groups are directed attached to an aromatic ring, and (iii) lithium hydroxide; (B) an allophanate catalyst; and (C) an organic compound which contains at least one hydroxyl group.

RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 09/002,308 filed in the United States Patent and Trademark Office onDec. 31, 1997 now U.S. Pat. No. 5,955,609.

BACKGROUND OF THE INVENTION

This invention relates to a novel trimerization catalyst system and to aprocess for the trimerization of isocyanates in the presence of thiscatalyst system. The catalyst system comprises (A) a lithium compoundselected from the group consisting of: (i) lithium salts of aliphatic oraromatic mono- or dicarboxylic acids, (ii) lithium salts of hydroxylgroup containing compounds having from 1 to 3 hydroxyl groups percompound, wherein the hydroxyl groups are directly attached to anaromatic ring, and (iii) lithium hydroxide; (B) an allophanate catalyst;and (C) an organic compound containing at least one hydroxyl group.

The trimerization of isocyanates to form polyisocyanurates is well knownin the art. Trimerization catalysts described in the prior art includealkali carboxylates as described in DE-OS 3,219,608, basic alkali metalsalts complexed with acyclic organic compounds as described in U.S. Pat.No. 4,379,905, basic alkali metal salts complexed with crown ethers asdescribed in U.S. Pat. No. 4,487,928, and combinations of tertiaryamines with specific quaternary ammonium salts as described in U.S. Pat.No. 3,954,684.

Catalysts described in U.S. Pat. Nos. 4,632,785 and 4,540,781 comprisealkali metal salts or quaternary ammonium salts of carboxylic acids ofthe formulas ##STR1## wherein R¹ is alkyl having from 2 to 8 carbonatoms, R² is a highly branched alkyl having from 3 to 8 carbon atoms, R³is selected from the group consisting of hydrogen, alkyl, and aryl, R⁴is selected from the group consisting of alkyl, aryl, aralkyl, andcycloalkyl, R⁵ is independently selected from aryl, and M⁺ is a cationselected from the group consisting of alkali metal cations andquaternary ammonium cations of a specific formula.

Canadian Patent Application 2,113,890 relates to trimer catalyst systemsfor aliphatic and aromatic isocyanates. The trimer catalyst systems ofthis earlier application comprise (A) a lithium compound selected fromthe group consisting of: (i) lithium salts of aliphatic or aromaticmonocarboxylic or dicarboxylic acids, (ii) lithium salts of hydroxylgroup containing compounds containing from 1 to 3 hydroxyl groups percompound, wherein the hydroxyl groups are directly attached to anaromatic ring, and (iii) lithium hydroxide; and (B) an organic compoundcontaining at least one hydroxyl group.

Advantages of the presently claimed catalyst systems in comparison tothe catalyst systems of Canadian Patent Application 2,113,890 includethe fact that the reaction is difficult to control using these earliercatalyst systems because the rate of reaction increases with the time,and thus results in runaway reactions. The novel catalyst systems of thepresent application, which contain an allophanate catalyst, providesteady and predictable rates of reaction which do not changesignificantly as the length of reaction time increases, i.e., thesereactions are smooth and "well-behaved". In addition, catalyst systemsof the present application work well at lower temperatures (i.e., ≦100°C.) than the catalyst systems of my earlier copending application.

DESCRIPTION OF THE INVENTION

This invention relates to a novel catalyst system and to a process forthe preparation of a polyisocyanate or a diisocyanate having anisocyanurate structure, wherein the trimer catalyst is this novelcatalyst system. These isocyanurate containing di- and/orpolyisocyanates may optionally contain urethane groups and/orallophanate groups in addition to the isocyanurate groups.

The trimerization catalyst system comprises:

(A) a compound selected from the group consisting of

(i) lithium salts of aliphatic or aromatic monocarboxylic acids ordicarboxylic acids,

(ii) lithium salts of hydroxyl group containing compounds containingfrom 1 to 3 hydroxyl groups per compound, wherein the hydroxyl groupsare attached directly to an aromatic ring,

(iii) lithium hydroxide, and

(iv) mixtures thereof;

(B) at least one allophanate catalyst; and

(C) at least one organic compound containing at least one hydroxylgroup.

The process for the preparation of a polyisocyanurate having anisocyanurate structure comprises

1) heating a compound selected from the group consisting of an organicpolyisocyanate, an organic isocyanate, or mixtures thereof, to atemperature of from about 50 to about 200° C., preferably from about 80to about 120° C., for a time period of from about 1 to about 500minutes, preferably from about 20 to about 240 minutes, in the presenceof a catalytic amount of

(A) a compound selected from the group consisting of

(i) lithium salts of aliphatic or aromatic monocarboxylic acids ordicarboxylic acids,

(ii) lithium salts of hydroxyl group containing compounds containingfrom 1 to 3 hydroxyl groups per compound, wherein the hydroxyl groupsare attached directly to an aromatic ring,

(iii) lithium hydroxide, and

(iv) mixtures thereof;

(B) at least one allophanate catalyst; and

(C) at least one organic compound containing at least one hydroxylgroup.

Once the organic polyisocyanate or diisocyanate mixture reaches thedesired NCO group content, it is preferred that a catalyst stopper isadded to the mixture in the ratio of 2 equivalents of the catalyststopper to each mole of catalyst present.

According to the present invention, the molar ratio of allophanatecatalyst to lithium salt is dependent on the particular isocyanate beingtrimerized. Without wishing to be bound by any particular theory, itappears that the reason for this is due to the fact that a small amountof urethane groups are needed for the catalyst system/package to work.If too little urethane is present, very little to no trimer is formed,and if too much urethane is present, the reaction becomes more difficultto control, and exhibits a greater tendency to runaway. Therefore, themolar ratio of the lithium trimer catalyst component to the allophanatecatalyst component varies relative to the isocyanate used since eachisocyanate has its own equilibrium between urethane and allophanate atany given catalyst mix. The hydroxyl group containing organic compoundis typically present in a quantity such that there are from about 0.006to about 0.2 equivalent hydroxyl groups per equivalent of isocyanate tobe trimerized, for all allophanate/trimer catalyst molar ratios. It ispreferred that at least 50%, more preferably at least 80%, of theequivalents of the hydroxyl groups present in the organic compound whichcontains hydroxyl groups are converted to allophanate groups in thefinal product. Most preferably, at least 90% of the equivalents of thehydroxyl groups present in the organic compound which contains hydroxylgroups are converted to allophanate groups. Ultimately, however, theseamounts are controlled by the catalyst ratios as discussed above. Inaddition, to minimize the urethane group content in the final product,once the desired amount of trimer is attained, additional allophanatecatalyst may be added to convert the urethane groups to allophanategroups.

Suitable catalyst stoppers for use in the present invention includeacidic materials such as, for example, anhydrous hydrochloric acid,sulfuric acid, bis(2-ethylhexyl) hydrogen phosphate, benzoyl chloride,Lewis acids and the like. The catalyst stopper is added to the reactionmixture after the desired NCO group content is reached. Catalyststoppers are added in a ratio of 2 equivalents of catalyst stopper toeach mole of catalyst present.

One preferred embodiment of the present invention requires hexamethylenediisocyanate (HDI) as the isocyanate being trimerized. In thisembodiment, the molar ratio of the allophanate catalyst (B) to thelithium compound (A) is from 1.0:1.0 up to 25.0:1.0. Based on this, itis preferred to use between 5×10⁻⁶ to 5×10⁻⁴ mole of lithium compound(A) in conjunction with from 0.006 to 0.2 equivalent hydroxyl groupsfrom the organic compound containing at least one hydroxyl group (C),per equivalent of isocyanate of the HDI to be trimerized. It is mostpreferred to use from about 1×10⁻⁵ to 1×10⁴ mole of lithium compound(A), with the appropriate amount of allophanate catalyst as describedabove, and to use from 0.02 to 0.10 equivalent hydroxyl groups from theorganic compound containing at least one hydroxyl group (C), perequivalent of isocyanate of the HDI to be trimerized.

Another preferred embodiment of the present invention is when theisocyanate to be trimerized is diphenylmethane diisocyanate (MDI). Inthis embodiment, the molar ratio of the lithium compound (A) to theallophanate catalyst (B) is from 4.0:1.0 up to 40.0:1.0. Based on this,it is preferred to use between 1×10⁻⁶ to 1×10⁵ mole of allophanatecatalyst (B) in conjunction with from 0.006 to 0.2 equivalent hydroxylgroups from the organic compound containing at least one hydroxyl group(C), per equivalent of isocyanate of the MDI to be trimerized. It ismost preferred to use from about 3×10⁻⁶ to 8×10⁻⁶ mole of allophanatecatalyst (B), with the appropriate amount of lithium compound (A) asdescribed above, and from 0.02 to 0.10 equivalent hydroxyl group fromthe organic compound containing at least one hydroxyl group (C), perequivalent of isocyanate of the MDI to be trimerized.

Another preferred embodiment of the present invention is when toluenediisocyanate (TDI) is the isocyanate being trimerized. In this case, themolar ratio of allophanate catalyst (B) to lithium compound (A) is from20:1 to 1:20. Based on this, it is preferred to use between 1×106 to4×10⁻⁵ mole of allophanate catalyst (B) in conjunction with 0.006 to 0.2equivalent hydroxyl groups from the organic compound which contains atleast one hydroxyl group (C), per equivalent of isocyanate of the TDI tobe trimerized. It is most preferred to use from about 5×10⁻⁶ to 3.2×10⁻⁵mole of allophanate catalyst (B) with the appropriate amount of lithiumcompound (A) as described above, and 0.02 to 0.10 equivalent hydroxylgroup of the organic compound containing at least one hydroxyl group(C), per equivalent of isocyanate of the TDI to be trimerized. The TDIproducts of the present application are not freeze-stable.

It has also been found that certain TDI products are freeze-stableliquids when greater than 0.015 equivalent hydroxyl groups of theorganic compound containing at least one hydroxyl group, i.e., component(C), of the above-identified catalyst system are used in the process ofthis invention. These freeze-stable liquids are not, however, thesubject of the present invention. Rather, these freeze-stable liquidsare the subject of applicants' copending application, application Ser.No. 09/001,843 which was filed in the United States Patent and TrademarkOffice on the same day as the present application, Dec. 31, 1997.

As used herein, the term "freeze-stable" refers to a product in whichsolids do not precipitate or settle out of when stored at 25° C. for 4weeks or longer. Some products which are "freeze-stable" may containfine solids. However, these fine solids do not settle out of the productunder the specified conditions.

Suitable lithium compounds (A)(i) for use in the present inventioninclude, for example, both the monolithium and dilithium salts ofaliphatic and aromatic carboxylic acids containing a total of from about1 to 36 carbon atoms. Both the mono- or dicarboxylic acids are suitablefor the process according to the invention. Examples of these lithiumcompounds include lithium formate, lithium salicylate, lithium acetate,lithium stearate, lithium propanate, lithium butyrate, lithium lactate,lithium laurate, lithium benzoate, lithium p-hydroxybenzoate, lithium4-hydroxyphenylacetate, monolithium salt of oxalic acid, dilithium saltof oxalic acid, monolithium salt of glutaric acid, dilithium salt ofglutaric acid, monolithium salt of isophthalic acid, dilithium salt ofisophthalic acid, monolithium salt of phthalic acid, dilithium salt ofphthalic acid, monolithium salt of terephthalic acid, and dilithium saltof terephthalic acid. Of these salts, lithium salicylate, lithiumacetate, and lithium stearate are preferred.

The lithium compound may also be, for example, (A)(ii) the lithium saltof a hydroxy group containing compound wherein the hydroxyl groups aredirectly attached to an aromatic ring. These compounds may contain from1 to 3 hydroxyl groups each, and the aromatic ring system contains atotal of from 6 to 18 carbon atoms. The aromatic ring system may be asingle ring such as, for example, phenyl, or a polynuclear aromaticsystem such as, for example, naphthalene. Suitable compounds include,for example, lithium phenoxide, 4-methyl lithium phenoxide, 2-hydroxylithium phenoxide, 3-hydroxy lithium phenoxide, 4-hydroxy lithiumphenoxide, lithium 1-naphthoxide, lithium 2-naphthoxide, etc. Lithiumsalts of cresols are also suitable trimerization catalysts.Theoretically, the lithium salts of substituted aromatic compounds aresuitable provided the substituents do not deactivate the ring so that itis no longer an effective trimerization catalyst.

Lithium hydroxide is suitable for use as component (A)(iii) in thepresent invention.

Lithium salts of mono- and di-carboxylic acids (component (A)(i)) arereadily obtained using standard preparative methods well known to oneskilled in the art. Equation (1) represents a general preparativemethod.

    R.sub.1 COOH+LiA→R.sub.1 COO.sup.- Li.sup.+ +AH     (1)

wherein: R₁ represents hydrogen or an aliphatic hydrocarbon chain havingfrom 1 to 35 carbon atoms, or an aromatic ring system having from 6 to18 carbon atoms, and

A represents an anion such as hydroxyl, hydride, alkoxide, etc.

The reactant LiA is used in an amount which is slightly less than molarequivalency, thereby ensuring that no residual reactant will remain inthe products.

The lithium salts of hydroxyl group containing compounds wherein thehydroxyl groups are directly attached to an aromatic ring (component(A)(ii)) can be prepared by a typical acid base reaction, followed bythe distillation of water, methanol, etc. However, the base must bestronger than the anion of the hydroxyl group of the aromatic compound.For example, lithium phenoxide can be prepared by reacting phenol withlithium hydroxide or lithium methoxide.

Suitable carboxylic acids for the preparation of the lithium salts(A)(i) include, for example, those aliphatic carboxylic acids havingfrom about 1 to about 36 carbon atoms, and aromatic carboxylic acidswherein the aromatic ring system has from 6 to 18 carbon atoms. Thealiphatic carboxylic acids may be either branched or straight chain, andeither saturated or unsaturated. Both aliphatic and aromaticmonocarboxylic acids and dicarboxylic acids are suitable. Some examplesof these include formic acid, acetic acid, propionic acid, stearic acid,lactic acid, benzoic acid, salicylic acid, lauric acid, glutaric acid,p-hydroxybenzoic acid, phthalic acid, isophthalic acid, and terephthalicacid. Theoretically, any compound having the carboxylic acid group wouldbe suitable provided any additional substituents do not interfere withthe formation of the salt.

Hydroxyl group containing compounds having at least one hydroxyl groupattached directly to an aromatic ring which are suitable for thepreparation of lithium salts (A)(ii) include, for example, thosearomatic alcohols containing from about 6 to 18 carbon atoms, andcontaining from 1 to 3 hydroxyl groups present per aromatic ring.Examples of these aromatic compounds include phenol, m-cresol,resorcinol, hydroquinone, catechol, 1-naphthol, 2-naphthol,4-methoxy-1-naphthol, 1-methoxy-2-naphthol, 1-nitro-2-naphthol,4-nitro-1-naphthol, 4-chloro-1-naphthol, 1-chloro-2-naphthol,hydroxyanthracene, hydroxyphenanthrene, isomeric methoxyphenols,nitrophenols, chlorophenols, etc.

According to the present invention, these lithium compounds (A) are tobe used in conjunction with (B) an allophanate catalyst and (C) anorganic compound which contains at least one hydroxyl group.

Suitable allophanate catalysts include metal carboxylates and metalacetylacetonates. Some examples of suitable allophanate catalysts forthe present invention include zinc octoate, tin-2-ethylhexanoate, zincacetylacetonate, zinc-2-ethylhexanoate, cobalt linoresinate, leadnaphthenate, lead 2-ethylhexanoate, lead linoresinate, cobalt2-ethylhexanoate, cobalt naphthenate, etc. Preferred allophanatecatalysts are zinc octoate, tin octoate, zinc-2-ethylhexanoate,tin-2-ethylhexanoate, and zinc acetylacetonate.

Suitable organic compounds containing at least one hydroxyl group (C)are also necessary according to the present process. Suitable compoundsinclude those compounds having a molecular weight in the range of from32 to about 6,000 and containing from 1 to 4 hydroxyl groups.

It is preferred that these organic compounds containing at least onehydroxyl group are lower molecular weight organic compounds containingfrom 1 to 4, more preferably 1 to 2 hydroxyl groups, and having amolecular weight range of from 32 to about 400. Suitable organiccompounds include, for example, methanol, 1-ethanol, 1,2-ethanediol,1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, n-amylalcohol, sec-amyl alcohol, tert-amyl alcohol, 1-ethyl-1-propanol,n-hexanol and isomers thereof, n-octyl alcohol, 2-octyl alcohol,2-ethyl-1-hexanol, n-decyl alcohol, n-dodecyl alcohol, neopentylglycol,n-tetradecyl alcohol, n-hexadecyl alcohol, n-octadecyl alcohol,1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol,3-methyl-2-butanol, 3,3-dimethyl-1-butanol, 2-ethyl-1,3-hexanediol,glycerol, 1,2,4-butanetriol, pentaerythritol, diethylene glycol,dipropylene glycol, diethylene glycol, triethylene glycol, etc. It ismore preferred for these organic compounds to contain from 1 to 2hydroxyl groups, such as a monoalcohol or a diol, and have a molecularweight of from 60 to about 200. Examples include 1-propanol, 2-propanol,1-butanol, 2-butanol, n-amyl alcohol, 1-methyl-butyl alcohol,1-ethyl-1-propanol, n-octyl alcohol, 2-octyl alcohol, 2-ethyl-1-hexanol,neopentyl-glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol,1,3-butanediol, 2,3-butanediol, 2-ethyl-1,3-hexanediol, diethyleneglycol, triethylene glycol, dipropylene glycol, tripropylene glycol,etc. Most preferred compounds are isomeric butanols, isomeric propanols,1,3-butanediol and 1,2-propanediol.

In addition to the lower molecular weight organic compounds containingat least one hydroxyl group identified above, higher molecular weightadducts of these low molecular weight compounds are also suitable to beused as component (C) of the present invention. These relatively highmolecular weight polyether polyols include those conventionally used inpolyurethane chemistry, and can be prepared by the epoxidation of a lowmolecular weight organic compound in the presence of a suitable catalystto yield a higher molecular weight adduct. Suitable polyether polyolstypically have molecular weights in the range of from greater than 400to about 6,000, preferably about 500 to about 3,000, more preferablyabout 500 to about 2,000. It is preferred that these polyether polyolshave a functionality of 1 to 3.

Suitable polyethers are known and may be prepared, for example, by thepolymerization of epoxides, optionally in the presence of a catalystsuch as BF₃, or by chemical addition of such epoxides, optionally asmixtures or successively, to starting components containing reactivehydrogen atoms. Suitable epoxides include ethylene oxide, propyleneoxide, butylene oxide, tetrahydrofuran, styrene oxide, orepichlorohydrin. Suitable starter components include water, alcohols, oramines, including, for example, ethylene glycol, 1,2- or1,3-propanediol, 1,2-, 1,3-, or 1,4-butanediol, trimethylolpropane,4,4'-dihydroxydiphenylpropane, aniline, glycerine, ammonia andethanolamine. Polyethers that contain predominantly primary hydroxylgroups (up to about 90% by weight, based on all of the hydroxyl groupsin the polyether) are also often preferred. Also suitable arepolybutadienes containing hydroxyl groups, and polyalkylene polyethers,such as polyoxyethylene diol, polyoxypropylene diol, polyoxybutylenediol, and polytetramethylene diol.

It is, of course, also possible to use a mixture of one or more of therelatively high molecular weight organic compounds containing at leastone hydroxyl group, with one or more of the relatively low molecularweight organic compounds containing at least one hydroxyl group.

Suitable polyisocyanates to be trimerized according to the presentinvention, to yield polyisocyanates having an isocyanurate structure,include the known aliphatic, cycloaliphatic, araliphatic, aromatic, andheterocyclic polyisocyanates, and mixtures thereof. Examples of thesepolyisocyanates include those described by W. Siefen in Justus LiebigsAnnalen der Chemie, 562, pages 75 to 136. More specifically, suitablepolyisocyanates include, but are not limited to,2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, diphenylmethane-4,4-diisocyanate, naphthylene-1,5-diisocyanate,hexamethylene-1,6 diisocyanate,1-isocyanato-3,5,5-trimethyl-5-isocyanato-methyl-cyclohexane,1,12-dodecane diisocyanate, cyclobutane-1,3-diisocyanate,cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl cyclohexane (i.e.,isophorone diisocyanate), 2,4- and/or 2,6-hexahydro-toluylenediisocyanate, hexahydro-1,3-phenylene diisocyanate,hexahydro-1,4-phenylene diisocyanate, perhydro-2,4'- and/or4,4'-diphenylmethane diisocyanate, 1,3- and/or 1,4-phenylenediisocyanate, diphenylmethane-2,4'-diisocyanate,naphthalene-1,5-diisocyanate, triphenylmethane-4,4',4"-triisocyanate andpolyphenyl polymethylene polyisocyanates obtained by phosgenatinganiline/formaldehyde condensation products. Also suitable arepolyisocyanate adducts containing urea, biuret, urethane, allophanate,uretdione, or carbodiimide groups or isocyanurate rings. Preferredpolyisocyanates include aromatic and aliphatic isocyanates, withhexamethylene-1,6-diisocyanate, 2,4-diisocyanatotoluene,2,6-diisocyanatotoluene, and diphenyl methane-4,4'-diisocyanate, andmixtures thereof, being particularly preferred.

The following examples further illustrate details for the process ofthis invention. The invention, which is set forth in the foregoingdisclosure, is not to be limited either in spirit or scope by theseexamples. Those skilled in the art will readily understand that knownvariations of the conditions of the following procedures can be used.Unless otherwise noted, all temperatures are degrees Celsius and allparts are parts by weight.

EXAMPLES

The following materials were used in the working examples:

TDI: an isomeric mixture comprising 80% by weight of 2,4-toluenediisocyanate and 20% by weight of 2,6-toluene diisocyanate

MDI: an isomeric mixture comprising 98% by weight of4,4'-diphenylmethane diisocyanate and 2% by weight of2,4-diphenylmethane diisocyanate

HDI: 1,6-hexamethylene diisocyanate

LiSal: lithium salicylate; commercially available from K&K Laboratories

T9: tin 2-ethylhexanoate

Polyol A: a propylene glycol/propylene oxide/ethylene oxide adducthaving 20% terminal ethylene oxide, a functionality of 2 and an OHnumber of 28 (molecular weight=4000)

Polyol B: a propylene glycol/propylene oxide adduct having afunctionality of 2 and an OH number of 56 (molecular weight=2000)

Example 1

To a 500 ml 3-neck flask equipped with a stirrer, thermometer and gasbubble tube were added 389 parts TDI and 25.7 parts 1-butanol. Thereaction mixture was heated to 90° C. over about 15 minutes withnitrogen gas being bubbled through the solution. Once the temperature ofthis mixture reached 90° C., 0.024 part zinc acetyl-acetonate and 0.004part lithium salicylate were added. After 35 minutes at 90° C., 0.051part benzoyl chloride was added to the reaction mixture followed bycooling to 25° C. The clear, colorless liquid had an NCO content of30.7%. A gel permeation chromatography scan of the product showed thepresence of trimer and allophanate.

Example 2

Using the general procedure of Example 1 above, 350 parts TDI and 23.1parts 1-butanol were mixed and heated to 100° C. At 100° C., 0.038 parttin 2-ethylhexanoate (T9) and 0.009 part lithium salicylate were added.After 27 minutes at 100° C., 0.34 part benzoyl chloride was addedfollowed by cooling to 25° C. The clear, colorless liquid had an NCOcontent for 29.8%.

Example 3

Using the general procedure of Example 1 above, 362 parts TDI and 29parts Polyol B were mixed and heated to 90° C. At 90° C., 0.020 part T9and 0.005 part LiSal were added. After 2.5 hours at 90° C., 0.052 partbenzoyl chloride was added followed by cooling to 25° C. The clear,colorless liquid had an NCO content of 32.0%.

Example 4

Using the general procedure of Example 1, 341 parts TDI and 68.6 partsPolyol B were mixed and heated to 90° C. At 90° C., 0.022 part T9 and0.003 part LiSal were added. After 21/4 hours at 90° C., 0.051 partbenzoyl chloride was added followed by cooling to 25° C. The clear,colorless liquid had an NCO content of 28.5% and a viscosity at 25° C.of 9580 mPa·s.

Example 5

Using the general procedure of Example 1, 360 parts TDI and 3.6 parts1-butanol were mixed and heated to 100° C. At 100° C., 0.071 part T9 and0.018 part LiSal were added. After 6 hrs at 100° C., 0.306 part benzoylchloride was added followed by cooling to 25° C. The clear, colorlessliquid had an NCO content of 39.9%.

Example 6

Using the general procedure of Example 1, 338 parts TDI and 22.3 parts1-butanol were mixed and heated to 80° C. At 80° C., 0.019 part T9 and0.004 part LiSal were added. After 1.5 hrs. at 80° C., 0.06 part benzoylchloride was added followed by cooling to 25° C. The clear, colorlessliquid had an NCO content of 30.0% and a viscosity at 25° C. of 4400mPa·s.

Example 7

Using the general procedure of Example 1, 344 parts TDI and 15.1 parts1-butanol were mixed and heated to 100° C. At 100° C., 0.018 part LiSalwas added. After one minute the reaction mixture exothermed to 145° C.and after a few more seconds exothermed to over 200° C. and set-up inthe flask.

Example 8

Using the procedure of Example I, 667 parts TDI and 133 parts Polyol Awere mixed and heated to 100° C. At 100° C., 0.010 part LiSal was added.After 2 minutes the temperature began to rise. Cooling was applied tothe flask using cold water, however, the reaction temperature continuedto increase to 116° C. over the next 16 minutes. At this point, thereaction was stopped by the addition of 0.041 part benzoyl chloride. Theclear, colorless liquid had an NCO content 31.6%.

Example 9

Using the general procedure of Example 1, 759 parts TDI and 33.7 parts1-butanol were mixed and heated to 100° C. At 100° C., 0.041 part LiSaland 0.005 part T9 were added. After a minute the reaction temperaturehad increased to 108° C. at which time the flask was cooled with coldwater, however, the reaction temperature continued to increase. After anadditional two minutes with cooling the temperature had increased to111° C. At this time, the reaction was stopped by the addition of 0.1part benzoyl chloride. The clear, colorless liquid had an NCO content of39.5%.

Example 10

Using the general procedure of Example 1, 375 parts MDI and 17.2 parts1-butanol were mixed and heated to 90° C. At 90° C., 0.0036 part zincacetylacetonate and 0.0197 part LiSal were added. After 45 minutes at90° C., 0.042 part benzoyl chloride was added followed by cooling to 25°C. The resulting product had an NCO content of 24.0%.

Example 11

Using the general procedure of Example 1, 335 parts TDI and 14.8 parts1-butanol were mixed and heated to 100° C. At 100° C., 0.004 part T9 and0.018 part LiSal were added. After about 15 minutes at 100° C., 0.070part benzoyl chloride was added, followed by cooling to 25° C. Theclear, colorless liquid had an NCO content of 31.4%.

Example 12

Using the procedure of Example 1, 665 parts HDI and 29.3 parts 1-butanolwere mixed and heated to 100° C. At 100° C., 0.101 part T9 and 0.035part LiSal were added. Over the next 87 minutes, the NCO content slowlydropped to 36.5%. At this time, 0.255 parts di(2-ethylhexyl) phosphatewas added followed by cooling to 25° C.

Example 13

Using the general procedure of Example 1, 552 parts HDI and 24.3 parts1-butanol were mixed and heated to 150° C. At 150° C., 0.100 part T9 and0.014 part LiSal were added. Over the next 83 minutes, the NCO contentslowly dropped to 36.0%. At this time, 0.210 parts di(2-ethylhexyl)phosphate was added followed by cooling to 25° C.

Example 14

Using the general procedure of Example 1, 349 parts MDI and 16 parts1-butanol were mixed and heated to 90° C. At 90° C., 0.009 part zincacetylacetonate and 0.037 part LiSal were added. After 1 hour at 90° C.,0.051 part benzoyl chloride was added followed by cooling to 25° C. Theresulting product had an NCO content of 23.6%.

Example 15

Using the general procedure of Example 1, 374 parts MDI and 17.2 parts1-butanol were mixed and heated to 90° C. At 90° C., 0.039 part zincacetylacetonate and 0.021 part LiSal were added (Li:allophanate molarratio 0.98). After 45 minutes at 90° C., the reaction mixture had an NCOcontent of 27.0% (theoretical allophanate NCO was 27.1%). After anadditional 3.2 hours at 90° C., the NCO was 26.9%.

Although the invention has been described in detail in the foregoing forthe purpose of illustration, it is to be understood that such detail issolely for that purpose and that variations can be made therein by thoseskilled in the art without departing from the spirit and scope of theinvention except as it may be limited by the claims.

What is claimed is:
 1. A trimerization catalyst system comprising:(A) acompound selected from the group consisting of(i) lithium salts ofaliphatic or aromatic mono- or dicarboxylic acids, (ii) lithium salts ofhydroxyl group containing compounds having from 1 to 3 hydroxyl groupsper compound, wherein the hydroxyl groups are attached directly to anaromatic ring, and (iii) lithium hydroxide; (B) an allophanate catalyst;and (C) an organic compound containing at least one hydroxyl group.
 2. Atrimerization catalyst system for diphenylmethane diisocyanate, saidcatalyst system comprising:(A) a compound selected from the groupconsisting of(i) lithium salts of aliphatic or aromatic mono- ordicarboxylic acids, (ii) lithium salts of hydroxyl group containingcompounds having from 1 to 3 hydroxyl groups per compound, wherein thehydroxyl groups are attached directly to an aromatic ring, and (iii)lithium hydroxide; (B) an allophante catalyst and (C) and organiccompound containing at least one hydroxyl group, wherein the molar ratioof (A) to (B) is from 4.0:1.0 up to 40.0:1.0.
 3. The catalyst system ofclaim 2, wherein (B) is present in an amount of from 1×10⁻⁶ to 1×10⁻⁵mole, in conjunction with from 0.006 to 0.2 equivalent hydroxyl groupsof (C) said organic compound, per equivalent of isocyanate in thediphenylmethane diisocyanate present to be trimerized.
 4. Atrimerization catalyst system for 1,6-hexamethylene diisocyanate, saidcatalyst system comprising:(A) a compound selected from the groupconsisting of(i) lithium salts of aliphatic or aromatic mono- ordicarboxylic acids, (ii) lithium salts of hydroxyl group containingcompounds having from 1 to 3 hydroxyl groups per compound, wherein thehydroxyl groups are attached directly to an aromatic ring, and (iii)lithium hydroxide; (B) an allophanate catalyst; and (C) an organiccompound containing at least one hydroxyl group, wherein the molar ratioof (A) to (B) is from 1.0:1.0 up to 25.0:1.0.
 5. The catalyst system ofclaim 4, wherein (A) said lithium compound is present in an amount offrom 5×10⁻⁶ to 5×10⁻⁴ mole, in conjunction with from 0.006 to 0.2equivalent hydroxyl groups from (C) said organic compound, perequivalent of isocyanate of the 1,6-hexamethylene diisocyanate presentto be trimerized.
 6. A trimerization catalyst system for toluenediisocyanate, said catalyst system comprising:(A) a compound selectedfrom the group consisting of(i) lithium salts of aliphatic or aromaticmono- or dicarboxylic acids, (ii) lithium salts of hydroxyl groupcontaining compounds having from 1 to 3 hydroxyl groups per compound,wherein the hydroxyl groups are attached directly to an aromatic ring,and (iii) lithium hydroxide; (B) an allophanate catalyst; and (C) anorganic compound containing at least one hydroxyl group, wherein themolar ratio of (A) to (B) is from 20:1 to 1:20.
 7. The catalyst systemof claim 6, wherein (B) is present in an amount of from 1×10⁻⁶ to 4×10⁻⁵mole, in conjunction with 0.006 to 0.2 equivalent hydroxyl groups of (C)said organic compound, per equivalent of isocyanate in the toluenediisocyanate present to be trimerized.